It has long been known to use plastic foam in building blocks for insulation purposes, the blocks having tongues and/or grooves extending around the top, bottom and end faces which are for interengagement when laid in vertical courses to form a side wall.
In U.S. Pat. No. 2,683,980 to Krause of July 20, 1954 the wall is one block thick with central grooves around the block perimeter for the wood frame members which run horizontally.
A similar expedient is proposed in U.S. Pat. No. 3,220,151 of Nov. 30, 1965 to Goldman wherein a pair of foam panels come together to form a block with central vertical voids and cement is poured into the voids to form the framework.
A single block of foam plastic having tongue and groove configuration around its perimeter and central voids for receiving cement is disclosed in U.S. Pat. No. 3,410,044 to Moog of Nov. 12, 1968.
A "foam form" product of Foam-form Canada Limited, 100 Canadian Road, Scarborough, Ontario, Canada is also known. It makes use of a plurality of polystyrene foam blocks to retain poured "in place" concrete with the help of horizontal reinforcing steel. Each foam block consists of a pair of panels permanently connected by steel mesh connectors extending across a gap which receives the poured cement and each panel has tongue and groove interlock edges extending therearound.